1. Field of the Invention
The present invention relates to a technique to perform die bonding of a semiconductor chip on a lead frame of a semiconductor device with a resin film used as a bonding material.
2. Description of the Background Art
FIGS. 10 and 11 are process diagrams schematically showing a method of bonding a semiconductor chip and a lead frame in a prior-art die bonding device. In both figures, reference numeral 110 denotes a dispenser head, numeral 111 denotes a resin paste, numeral 1 denotes a lead frame for semiconductor device (hereinafter, simply referred to as lead frame) and numeral 2 denotes a semiconductor chip (hereinafter, simply referred to as chip).
First, a transport device (not shown) and a positioning device (not shown) for the lead frame provided in the prior-art die bonding device positions the lead frame 1 at a required position and then the dispenser head 110 guided in a transportable manner above a predetermined region in a bonding pad of the lead frame 1 applies an appropriate amount of resin paste 111 onto the predetermined region (see FIG. 10).
Next, a chip transfer head (not shown) places the chip 2 on the resin paste 111 applied on the lead frame 1 and applies a required load onto the chip 2 to evenly spread the resin paste 111 between a lower surface of the chip 2 and an upper surface of the lead frame 1, thereby temporarily bonding the chip 2 and the lead frame 1 (see FIG. 11). Then, by the above bonding method, similarly, a plurality of chips 2 are temporarily bonded on the lead frame 1.
After that, for each lead frame 1, the resin paste 111 is dried in a later curing process to completely bond the chips 2 on the lead frame 1.
Since the prior-art die bonding device has a constitution for bonding the chip and the lead frame by application of the resin paste, the following roughly-divided two problems (1) and (2) arise.
(1) The first problem lies in that the prior-art bonding method has high probability of creating a void 120 by sucking air into the resin paste 111, as illustrated in FIG. 12, at the same time when the required load is put on the resin paste 111 to evenly apply the paste 111 between the lower surface of the chip 2 and the upper surface of the lead frame 1 in temporary bonding of the chip 2 on the lead frame 1 with the resin paste 111 put therebetween. When the void 120 is produced and left inside the resin paste 111, the following ill effect may be caused after sealing the chip 2, inner lead portions (not shown) of the lead frame 1 and the like with a mold resin (not shown). Specifically, when the chip 2 and the like generate heat due to an operation of the semiconductor device, this heat generation raises the temperature of the resin 111 existing between the lower surface of the chip 2 and the upper surface of the lead frame 1. As a result, the void 120 (of FIG. 12) which is babble expands and it is worried that there arises an ill effect that the chip 2 is distorted or damaged by a stress due to this expansion. Further, it is also worried that the expansion force of the void 120 causes a crack in the peripheral mold resin which seals the chip 2 and the like, resulting in an imperfect sealing. Therefore, so long as such an ill effect is expected, there is great necessity of preventing the void 120 from appearing.
(2) The second problem is caused by that it is not sure in which direction the resin paste 111 (of FIG. 11) used in the prior art spreads when the load is applied from above through the chip 2, i.e., unevenness in spreading direction of the resin paste 111 on applying the load. Therefore, if the resin paste 111 spreads one-sidedly when the load is applied, as shown in FIG. 12, for example, there may arise a problem that an extending-off portion 112 of the resin paste 111 is developed on one side-surface side from the lower surface of the chip 2. This extending-off portion 112 also causes the following ill effect. (a) First arises a problem that a sealing region is reduced by the extending-off portion 112 and the thickness of the mold resin may be partially thinned depending on where the chip 2 having the extending-off portion 112 is placed. (b) Second, when the extending-off portion 112 rises up to near the surface of the chip 2, a wire (not shown) and the extending-off portion 112 may come into contact with each other in a wire bonding process for the chip 2. At this time, if the resin paste 111 is a pure insulative substance, no problem arises, but the resin paste 111 including silver, for example, is often used and in this case, the paste 111 and the wire become conducting. (c) Third, as shown in FIG. 12, a clearance 113 tends to appear on the other end side of the chip 2 and in a later sealing process, the mold resin enters the clearance 113 to weaken the bonding strength between the chip 2 and the lead frame 1, so that it is worried that the chip 2 tends to be removed off. (d) Additionally, as shown in FIG. 12, the chip 2 is not bonded in parallel to the surface of the lead frame 1 and like the case of (c), that weakens the bonding strength between the chip 2 and lead frame 1, and the mold resin layer over an upper surface of the chip 2 is thinned by the inclination of the chip 2, which may cause a problem in terms of hermeticity. Therefore, there is great necessity of preventing the extending-off portion 112 from appearing.
The present invention is directed to a die bonding device. According to a first aspect of the present invention, the die bonding device comprises: a supply unit configured to generate a strap-like resin film from a resin film having stickiness on its back surface and a predetermined thickness, the strap-like resin film having first and second widths in first and second directions, respectively, and the predetermined thickness; a transport unit configured to transport the strap-like resin film to a predetermined region in a surface of a lead frame to bring the back surface of the strap-like resin film into contact with the predetermined region; a heating unit configured to set the temperature of the strap-like resin film to be higher than the room temperature and below the transition temperature of the strap-like resin film; and a pressurizing unit having a pressing portion which is vertically movable, the pressurizing unit configured to pressurize the strap-like resin film from a surface thereof heated by the heating unit, with the pressing portion, to bond the back surface of the strap-like resin film to the predetermined region, and in the die bonding device of the first aspect, the predetermined region has the first and second widths in the first and second directions, respectively.
According to a second aspect of the present invention, in the die bonding device according to the first aspect, the resin film comprises a resin ribbon whose stickiness at the room temperature is lower than that at the transition temperature; and a cover ribbon layered on a surface of the resin ribbon and having a surface of non-stickiness, the strap-like resin film comprises a strap-like resin ribbon; and a strap-like cover ribbon layered on a surface of the strap-like resin ribbon, and the pressing portion of the pressurizing unit pressurizes a surface of the strap-like cover ribbon layered on the surface of the strap-like resin ribbon whose temperature is set to be higher than the room temperature and below the transition temperature of the strap-like resin ribbon, to bond a back surface of the strap-like resin ribbon to the predetermined region, and defining the transport unit, the heating unit, the pressurizing unit and the pressing portion as a first transport unit, a first heating unit, a first pressurizing unit and a first pressing portion, respectively, the die bonding device further comprises: a removing unit configured to remove only the strap-like cover ribbon included in the strap-like resin film in which the back surface of the strap-like resin ribbon is bonded to the predetermined region; a second heating unit configured to set the temperature of the strap-like resin ribbon in a predetermined temperature range including the transition temperature of the strap-like resin ribbon; a second transport unit configured to transport a semiconductor chip having the first and second widths in the first and second directions, respectively, onto the surface of the strap-like resin ribbon without the strap-like cover ribbon; and a second pressurizing unit having a second pressing portion which is vertically movable, the second pressurizing unit configured to pressurize the strap-like resin ribbon heated by the second heating unit and the semiconductor chip transported onto the surface of the strap-like resin ribbon from a surface of the semiconductor chip with the second pressing portion, to bond a back surface of the semiconductor chip to the surface of the strap-like resin ribbon.
According to a third aspect of the present invention, in the die bonding device according to the first aspect, the resin film is made of a resin ribbon whose stickiness at the room temperature is lower than that at the transition temperature, the strap-like resin film is made of a strap-like resin ribbon, and the pressing portion of the pressurizing unit has a pressing surface of non-stickiness and pressurizes a surface of the strap-like resin ribbon whose temperature is set to be higher than the room temperature and below the transition temperature of the strap-like resin ribbon by the heating unit, with the pressing surface interposed, to bond a back surface of the strap-like resin ribbon to the predetermined region.
According to a fourth aspect of the present invention, in the die bonding device according to the third aspect, defining the transport unit, the heating unit, the pressurizing unit and the pressing portion as a first transport unit, a first heating unit, a first pressurizing unit and a first pressing portion, respectively, the die bonding device further comprises: a second heating unit configured to set the temperature of the strap-like resin ribbon in a predetermined temperature range including the transition temperature of the strap-like resin ribbon; a second transport unit configured to transport a semiconductor chip having the first and second widths in the first and second directions, respectively, onto the surface of the strap-like resin ribbon; and a second pressurizing unit having a second pressing portion which is vertically movable, the second pressurizing unit configured to pressurize the strap-like resin ribbon heated by the second heating unit and the semiconductor chip transported onto the surface of the strap-like resin ribbon from a surface of the semiconductor chip with the second pressing portion, to bond a back surface of the semiconductor chip to the surface of the strap-like resin ribbon.
According to a fifth aspect of the present invention, in the die bonding device according to the second aspect, the second pressing portion of the second pressurizing unit has such shape and size as to collectively pressurize surfaces of a plurality of semiconductor chips each transported onto the surface of the strap-like resin ribbon corresponding thereto by the second transport unit.
According to a sixth aspect of the present invention, in the die bonding device according to the fifth aspect, the second pressurizing unit further comprises an interference material of non-stickiness, having a predetermined elastic force in a direction of thickness and provided between the position of the second pressing portion before pressurization and the surfaces of the plurality of semiconductor chips, and the second pressing portion of the second pressurizing unit pressurizes the surfaces of the plurality of semiconductor chips with the interference material interposed.
According to a seventh aspect of the present invention, in the die bonding device according to the fourth aspect, the second pressing portion of the second pressurizing unit has such shape and size as to collectively pressurize surfaces of a plurality of semiconductor chips each transported onto the surface of the strap-like resin ribbon corresponding thereto by the second transport unit.
According to an eighth aspect of the present invention, in the die bonding device according to the seventh aspect, the second pressurizing unit further comprises an interference material of non-stickiness, having a predetermined elastic force in a direction of thickness and provided between the position of the second pressing portion before pressurization and the surfaces of the plurality of semiconductor chips, and the second pressing portion of the second pressurizing unit pressurizes the surfaces of the plurality of semiconductor chips with the interference material interposed.
According to a ninth aspect of the present invention, in the die bonding device according to the second aspect, the removing unit has a flexible body having a first surface of stickiness and a second surface of non-stickiness opposed to the first surface, said flexible body provided above the strap-like ribbon, the removing unit configured to bend the flexible body to bond the first surface and the surface of the strap-like cover ribbon and forcedly return the bent flexible body to the initial position to remove the strap-like cover ribbon.
According to a tenth aspect of the present invention, in the die bonding device according to the first aspect, the supply unit comprises a pair of rollers configured to hold the resin film; and a blade portion positioned in a direction of sending the resin film through an operation of the pair of rollers, the blade portion configured to cut an edge portion of the resin film of a predetermined length sent through the operation of the pair of rollers to obtain the strap-like resin film, and at least one of the pair of rollers is a metal roller provided with a plurality of protrusion needles each having such a length as to reach a sticky portion of the resin film.
The present invention is also directed to a semiconductor device. According to an eleventh aspect of the present invention, the semiconductor device comprises: at least one semiconductor chip which is die-bonded onto the predetermined region by the die bonding device according to the second aspect.
The present invention is directed to a die bonding device again. According to a twelfth aspect of the present invention, the die bonding device comprises: supply means for generating a strap-like resin film from a resin film having stickiness on its back surface and a predetermined thickness, the strap-like resin film having first and second widths in first and second directions, respectively, and the predetermined thickness; transport means for transporting the strap-like resin film to a predetermined region in a surface of a lead frame to bring the back surface of the strap-like resin film into contact with the predetermined region; heating means for setting the temperature of the strap-like resin film to be higher than the room temperature and below the transition temperature of the strap-like resin film; and pressurizing means having a pressing portion which is vertically movable, the pressurizing means for pressurizing the strap-like resin film from a surface thereof heated by the heating means, with the pressing portion, to bond the back surface of the strap-like resin film to the predetermined region, in the die bonding device of the twelfth aspect, the predetermined region has the first and second widths in the first and second directions, respectively.
According to a thirteenth aspect of the present invention, in the die bonding device according to the twelfth aspect, the resin film comprises a resin ribbon whose stickiness at the room temperature is lower than that at the transition temperature; and a cover ribbon layered on a surface of the resin ribbon and having a surface of non-stickiness, the strap-like resin film comprises a strap-like resin ribbon; and a strap-like cover ribbon layered on a surface of the strap-like resin ribbon, and the pressing portion of the pressurizing means pressurizes a surface of the strap-like cover ribbon layered on the surface of the strap-like resin ribbon whose temperature is set to be higher than the room temperature and below the transition temperature of the strap-like resin ribbon, to bond a back surface of the strap-like resin ribbon to the predetermined region, and defining the transport means, the heating means, the pressurizing means and the pressing portion as first transport means, first heating means, first pressurizing means and a first pressing portion, respectively, the die bonding device further comprises: removing means for removing only the strap-like cover ribbon included in the strap-like resin film in which the back surface of the strap-like resin ribbon is bonded to the predetermined region; second heating means for setting the temperature of the strap-like resin ribbon in a predetermined temperature range including the transition temperature of the strap-like resin ribbon; second transport means for transporting a semiconductor chip having the first and second widths in the first and second directions, respectively, onto the surface of the strap-like resin ribbon without the strap-like cover ribbon; and second pressurizing means having a second pressing portion which is vertically movable, the second pressurizing means for pressurizing the strap-like resin ribbon heated by the second heating means and the semiconductor chip transported onto the surface of the strap-like resin ribbon from a surface of the semiconductor chip with the second pressing portion, to bond a back surface of the semiconductor chip to the surface of the strap-like resin ribbon.
According to a fourteenth aspect of the present invention, in the die bonding device according to the twelfth aspect, the resin film is made of a resin ribbon whose stickiness at the room temperature is lower than that at the transition temperature, the strap-like resin film is made of a strap-like resin ribbon, and the pressing portion of the pressurizing means has a pressing surface of non-stickiness and pressurizes a surface of the strap-like resin ribbon whose temperature is set to be higher than the room temperature and below the transition temperature of the strap-like resin ribbon by the heating means, with the pressing surface interposed, to bond a back surface of the strap-like resin ribbon to the predetermined region.
According to a fifteenth aspect of the present invention, in the die bonding device according to the fourteenth aspect, defining the transport means, the heating means, the pressurizing means and the pressing portion as first transport means, first heating means, first pressurizing means and a first pressing portion, respectively, the die bonding device further comprises: second heating means for setting the temperature of the strap-like resin ribbon in a predetermined temperature range including the transition temperature of the strap-like resin ribbon; second transport means for transporting a semiconductor chip having the first and second widths in the first and second directions, respectively, onto the surface of the strap-like resin ribbon; and second pressurizing means having a second pressing portion which is vertically movable, the second pressurizing means for pressurizing the strap-like resin ribbon heated by the second heating means and the semiconductor chip transported onto the surface of the strap-like resin ribbon from a surface of the semiconductor chip with the second pressing portion, to bond a back surface of the semiconductor chip to the surface of the strap-like resin ribbon.
According to a sixteenth aspect of the present invention, in the die bonding device according to the thirteenth aspect, the second pressing portion of the second pressurizing means has such shape and size as to collectively pressurize surfaces of a plurality of semiconductor chips each transported onto the surface of the strap-like resin ribbon corresponding thereto by the second transport means.
According to a seventeenth aspect of the present invention, in the die bonding device according to the sixteenth aspect, the second pressurizing means further comprises an interference material of non-stickiness, having a predetermined elastic force in a direction of thickness and provided between the position of the second pressing portion before pressurization and the surfaces of the plurality of semiconductor chips, and the second pressing portion of the second pressurizing means pressurizes the surfaces of the plurality of semiconductor chips with the interference material interposed.
According to an eighteenth aspect of the present invention, in the die bonding device according to the fifteenth aspect, the second pressing portion of the second pressurizing means has such shape and size as to collectively pressurize surfaces of a plurality of semiconductor chips each transported onto the surface of the strap-like resin ribbon corresponding thereto by the second transport means.
According to a nineteenth aspect of the present invention, in the die bonding device according to the eighteenth aspect, the second pressurizing means further comprises an interference material of non-stickiness, having a predetermined elastic force in a direction of thickness and provided between the position of the second pressing portion before pressurization and the surfaces of the plurality of semiconductor chips, and the second pressing portion of the second pressurizing means pressurizes the surfaces of the plurality of semiconductor chips with the interference material interposed.
According to a twentieth aspect of the present invention, in the die bonding device according to the thirteenth aspect, the removing means has a flexible body having a first surface of stickiness and a second surface of non-stickiness opposed to the first surface, said flexible body provided above the strap-like ribbon, the removing means for bending the flexible body to bond the first surface and the surface of the strap-like cover ribbon and forcedly return the bent flexible body to the initial position to remove the strap-like cover ribbon.
(1) In accordance with the first and twelfth aspects of the present invention, in bonding the strap-like resin film to the lead frame, it is advantageously possible to stably and reliably bond the back surface of the film to the predetermined region while preventing the film from extending off from the predetermined region of the lead frame and moreover pushing out a void which is mixed in the film to remove it from the film to thereby sufficiently suppress emergence of the void and its remainder.
(2) In accordance with the second and thirteenth aspects of the present invention, it is possible to effectively prevent a situation where the strap-like resin ribbon extends off from the predetermined region to attach to side surfaces of the semiconductor chip to even the ribbon in thickness and completely prevent the void from remaining in the strap-like resin ribbon, and as a result the semiconductor chip can be stably and reliably bonded onto the predetermined region, whereby a desired bonding strength can be obtained between the semiconductor chip and the strap-like resin ribbon and between the ribbon and the predetermined region.
Moreover, the above aspects of the present invention produce an effect that the pressing portion of the pressurizing unit can bond the back surface of the strap-like resin ribbon to the predetermined region with the cover ribbon not bonded thereto.
(3) In accordance with the third and fourteenth aspects of the present invention, an effect that the pressing portion of the pressurizing unit can effectively pressurize the strap-like resin ribbon without being bonded to the ribbon even when the resin film is made of the resin ribbon.
(4) In accordance with the fourth and fifteenth aspects of the present invention, it is possible to effectively prevent a situation where the strap-like resin ribbon extends off from the predetermined region to attach to the side surfaces of the semiconductor chip to even the ribbon in thickness and completely prevent the void from remaining in the strap-like resin ribbon, and as a result the semiconductor chip can be stably and reliably bonded onto the predetermined region, whereby a desired bonding strength can be obtained between the semiconductor chip and the strap-like resin ribbon and between the ribbon and the predetermined region even when the resin film is made of the resin ribbon.
(5) The fifth, seventh, sixteenth and eighteenth aspects of the present invention can remarkably improve the performance of the die bonding device.
(6) In accordance with the sixth, eighth, seventeenth and nineteenth aspects of the present invention, since pressure is indirectly applied with the interference material interposed, without any influence of variation in thicknesses of the plurality of semiconductor chips if there is, it is possible to stably and reliably pressurize the plurality of semiconductor chips in a collective manner and reliably protect the respective surfaces of the plurality of semiconductor chips.
(7) The ninth and twentieth aspects of the present invention can reliably and easily remove the strap-like cover ribbon.
(8) In accordance with the tenth aspect of the present invention, since a microscopic hole corresponding to the diameter of a protrusion needle which can reach the sticky portion of the resin film is formed in the film on the stage of sending the film off, the microscopic hole provides an out of the void mixed in the strap-like resin film, to thereby push much more void out.
(9) The eleventh aspect of the present invention realizes a semiconductor device of excellent characteristics and quality, with no problem caused by extending-off of the die bonding material or bonding material, or the void remaining inside the material.
An object of the present invention is to a die bonding technique to completely prevent extending-off of the resin paste and emergence of a void and enhance the bonding strength between a chip and a lead frame by interposing a resin film evenly spreading between a lower surface of the chip and an upper surface of the lead frame.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.